(a) Field of the Invention
The present invention relates to a digital cable television broadcasting system. More specifically, the present invention relates to a program and system information protocol (PSIP) converter for linking digital terrestrial broadcasting and digital satellite television broadcasting to a digital cable television broadcasting network in real-time, a PSIP converting method, and a digital cable television broadcasting system using the PSIP converter.
(b) Description of the Related Art
Currently, the Korean digital television broadcasting standards are classified into: terrestrial broadcasting on the Advanced Television Systems Committee (ATSC) basis, satellite broadcasting on the Digital Video Broadcasting (DVB) basis, and a cable broadcasting on the OpenCable basis, which is a temporary standard.
In this situation, it is very difficult to link terrestrial broadcasting or satellite broadcasting to a cable broadcasting network in real-time. This is because each broadcast's transport stream (TS) is commonly generated according to the international standard ISO/IEC 13818-1(MPEG-2 Part 1), but the protocol for transmitting program and system information is the PSIP in the case of terrestrial broadcasting, the protocol is a service information (SI) protocol in the case of satellite broadcasting, and the protocol is the PSIP which is identical with that of the terrestrial broadcasting but marginally differently applied compared with that of the terrestrial broadcasting in the case of cable broadcasting. Also, it is because the terrestrial broadcasting adopts the vestigial sideband (VSB) method, the satellite broadcasting adopts the quadrature phase shift keying (QPSK) method, and the cable broadcasting adopts the quadrature amplitude modulation (QAM) method in the modulation and demodulation method.
In particular, digital cable television broadcasting includes a method for transmitting the protocol and system information to an in-band channel for outputting broadcast TS, and a method for transmitting the same to an out-of-band channel for bi-directional data communication between a cable head-end and a subscriber.
The case of the cable broadcasting PSIP (this will be referred to as a cable PSIP hereinafter) that is marginally differently applied when compared to the terrestrial broadcasting corresponds to the in-band channel transmission method, and the out-of-band transmission method uses the SI protocol of the SCTE standard (this will be referred to as a cable SI hereinafter) to transmit the program and system information on all the currently output channels.
The above-noted cable SI protocol is totally different from the DVB standard satellite broadcasting SI protocol.
The cable SI protocol includes cable PSIP data, defined broadcasting network information, and modulation and demodulation method information.
Therefore, cable broadcasting service providers must transmit PSIP data to the in-band channel, and cable SI data to the out-of-band channel. Here, the case of transmitting the cable PSIP data to the in-band channel only applies to a free-of-charge channel such as a duty retransmission, and in the case of a charged channel, only the cable SI data are transmitted to the out-of-band channel. The cable SI data are to be transmitted to all channels in the charged and free-of-charge channel cases.
Since broadcasting has become digitalized, conversion of modulation and demodulation of broadcasting signals and rearrangement of channel frequencies used for re-transmitting terrestrial television broadcasting and satellite television broadcasting in conventional analog television broadcasting no longer satisfies digital broadcasting environments. Since actual linking of broadcasting networks is impossible, a protocol conversion for analyzing the broadcasting signals must be developed.